<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        html,body{
            width: 100%;
            height: 100%;
            margin: 0;padding: 0
        }
        .leftbox{
            width: 200px;
            height: 500px;
            background: #ccc;
            float: left;
        }
        .centerbox{
            /* width: 100% */
            height: 500px;
            background: pink;
            overflow: hidden;
        }
        .rightbox{
            width: 200px;
            height: 500px;
            background: skyblue;
            float: right; /* 块(只显示当前元素的大小区域) */
            
        }
    </style>
</head>
<body>
    <div class="leftbox">左</div>
    <div class="rightbox">右</div>
    <div class="centerbox">中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中中</div>
</body>
</html>